期刊
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
卷 399, 期 4, 页码 654-658出版社
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.bbrc.2010.07.137
关键词
Nitrosative stress; Anaerobic protozoa; Hemeprotein; Flavin; NO amperometry
资金
- Ministero dell'Istruzione, dell'Universita e della Ricerca of Italy [2008FJJHKM_002, RBFR08F41U_001]
- European Society of Clinical Microbiology and Infectious Diseases
Flavohemoglobins (flavoHbs), commonly found in bacteria and fungi, afford protection from nitrosative stress by degrading nitric oxide (NO) to nitrate. Giardia intestinalis, a microaerophilic parasite causing one of the most common intestinal human infectious diseases worldwide, is the only pathogenic proto-zoon as yet identified coding for a flavoHb. By NO amperometry we show that, in the presence of NADH, the recombinant Giardia flavoHb metabolizes NO with high efficacy under aerobic conditions (TN = 116 +/- 10 s(-1) at 1 mu M NO, T = 37 degrees C). The activity is [O-2]-dependent and characterized by an apparent K-M.O2 = 22 +/- 7 mu M. Immunoblotting analysis shows that the protein is expressed at low levels in the vegetative trophozoites of Giardia; accordingly, these cells aerobically metabolize NO with low efficacy. Interestingly, in response to nitrosative stress (24-h incubation with >= 5 mM nitrite) flavoHb expression is enhanced and the trophozoites thereby become able to metabolize NO efficiently, the activity being sensitive to both cyanide and carbon monoxide. The NO-donors S-nitrosoglutathione (GSNO) and DETA-NONOate mimicked the effect of nitrite on flavoHb expression. We propose that physiologically flavoHb contributes to NO detoxification in G. intestinalis. (C) 2010 Elsevier Inc. All rights reserved.
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